Abstract

Tree decline is a serious problem facing remnant Eucalypt forests and woodland ecosystems all over Australia (Keane et al, 2001). The causes of decline in some Western Australian Eucalyptus species have been intensively studied (e.g. Phytophthora cinnamomi on Eucalyptus marginata) while the causes of decline in other species are barely understood. Eucalyptus rudis (Flooded Gum) is a species typically found along watercourses, on floodplains and around wetlands. Eucalyptus rudis is declining across its range in the South West of Western Australia, and the symptoms are typical of those associated with Phytophthora, i.e. sparse small-sized foliage, production of epicormic shoots, crown dieback, extensive losses of fine roots, dieback of tap roots and necrotic lesions on small woody roots. Preliminary isolation tests have recovered Phytophthora species from declining E. rudis. This study reports on Phytophthora species associated with declining E. rudis from across a range of water bodies, soils, and vegetation types. Discussion will also cover the response of trees to phosphite and the results of preliminary pathogenicity studies.